Subject: Re: [boost] Boost.Algorithm design question
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-10-31 11:56:05
on Mon Oct 31 2011, "Peter Dimov" <pdimov-AT-pdimov.com> wrote:
> Dave Abrahams wrote:
>> I think you're missing the point, which is:
>
>>
>> When the specification for an algorithm exposes the actual expressions
>> used in a given implementation of an algorithm, it tends to lock down
>> the implementation in ways that don't necessarily make sense (and can
>> prevent optimizations). Tiny details that one usually doesn't
>> consider, like whether part of the expression is an lvalue or an
>> rvalue, const or non-const, become encoded into the specification of
>> the algorithm.
>
> None of this has anything to do with the fact that you want to require
> operator== to be an equivalence relation, and it doesn't have to be.
Again, missing my point.
I long ago stipulated that this algorithm could be useful even in places
where op== is not an equivalence relation, and that it was desirable to
support those uses. My instinct to require equivalence was part of a
reaction against writing the algorithm's specification in terms of valid
expressions. I think such specifications need to be given scrutiny than
they have been, historically.
-- Dave Abrahams BoostPro Computing http://www.boostpro.com